Method for forming a cast article

ABSTRACT

One embodiment of the present invention is a unique method for forming a cast porous article. Other embodiments include apparatuses, systems, devices, hardware, methods, and combinations for forming cast porous articles. Further embodiments, forms, features, aspects, benefits, and advantages of the present application shall become apparent from the description and figures provided herewith.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of U.S. Provisional PatentApplication No. 61/232,453, filed Aug. 9, 2009, and is incorporatedherein by reference.

FIELD OF THE INVENTION

The present invention relates generally to castings, and moreparticularly in one form to processing a porous cast article.

BACKGROUND

Casting technology, including casting porous articles, remains an areaof interest. Some existing systems have various shortcomings, drawbacks,and disadvantages relative to certain applications. Accordingly, thereremains a need for further contributions in this area of technology.

SUMMARY

One embodiment of the present invention is a unique method for forming acast porous article. Other embodiments include apparatuses, systems,devices, hardware, methods, and combinations for forming cast porousarticles. Further embodiments, forms, features, aspects, benefits, andadvantages of the present application shall become apparent from thedescription and figures provided herewith.

BRIEF DESCRIPTION OF THE DRAWINGS

The description herein makes reference to the accompanying drawingswherein like reference numerals refer to like parts throughout theseveral views, and wherein:

FIG. 1 is a system for freeform fabricating a casting mold in accordancewith an aspect of the present invention.

FIG. 2 illustrates a casting mold in accordance with an embodiment ofthe present invention.

FIG. 3 is an enlarged partial cross section through an airfoil portionof the casting mold of FIG. 2.

FIG. 4 schematically depicts a cross section of a blade casting producedin accordance with an embodiment of the present invention.

FIG. 5 schematically depicts a cross section of the blade casting of theembodiment of FIG. 4.

FIG. 6 schematically depicts a cross section of a blade casting producedin accordance with an embodiment of the present invention.

FIG. 7 schematically depicts a cross section of the blade casting of theembodiment of FIG. 6.

DETAILED DESCRIPTION

For purposes of promoting an understanding of the principles of theinvention, reference will now be made to the embodiments illustrated inthe drawings, and specific language will be used to describe the same.It will nonetheless be understood that no limitation of the scope of theinvention is intended by the illustration and description of certainembodiments of the invention. In addition, any alterations and/ormodifications of the illustrated and/or described embodiment(s) arecontemplated as being within the scope of the present invention.Further, any other applications of the principles of the invention, asillustrated and/or described herein, as would normally occur to oneskilled in the art to which the invention pertains, are contemplated asbeing within the scope of the present invention.

Referring to FIG. 1, there is schematically illustrated a non-limitingexample of a freeform fabrication system 10 for freeform fabrication ofa component, such as a ceramic gas turbine engine blade, in accordancewith an embodiment of the present invention. Ceramic materialscontemplated herein include, but are not limited to, alumina, zirconia,silica, yittria, magnesia, and mixtures thereof. In one form, system 10is a selective laser activation (SLA) stereolithography system.Selective laser activation is based upon a stereolithography processthat utilizes resins which solidify when exposed to an energy dose. Inone form, the resin includes ceramic particles disposed within aphoto-polymerizable monomer(s) and/or oligomer(s), and the energy doseis a polymerizing energy dose. The present application contemplates theuse of an oligomer(s) resin alone or in combination with a monomerresin. Although the present application is described with respect to acomponent in the form of ceramic blade mold 12, it will be understoodthat the present application is also applicable to other types ofmaterials and to other types of components. While the presentapplication will be generally described with respect to an SLAstereolithography system, it is equally applicable to other freeformfabrication systems, such as flash cure systems and other forms ofscanned cure systems, as well as other freeform fabrication systems notmentioned herein.

System 10 is used to create gas turbine engine blade mold 12 as a threedimensional ceramic component formed of a plurality of layers, some ofwhich are labeled as layers 14, 16, 18 and 20. In one form,stereolithography system 10 employs a ceramic loaded resin 22, andincludes a resin containment reservoir 24, an elevation-changing member26, a laser source 28 and a scanning device 30 operative to scan a laserbeam 32 across elevation changing member 26. Resin containment reservoir24 is filled with a quantity of ceramic loaded resin 22 from whichcomponent 12 is fabricated. In one form, ceramic loaded resin 22contains a photoinitiator. In another form, ceramic loaded resin 22contains a dispersant, in addition to the photoinitiator. Scanningdevice 30 scans a laser beam 32 from laser source 28 across ceramicloaded resin 22, e.g., on a surface 34 ceramic loaded resin 22, in thedesired shape to form each layer of gas turbine engine blade mold 12.The ceramic particles contained in ceramic loaded resin 22 ultimatelyform the completed mold 12.

A three dimensional coordinate system including a first axis, a secondaxis and a third axis is utilized as a spatial reference for the itembeing fabricated, e.g., ceramic mold 12. In one form, thethree-dimensional coordinate system is a Cartesian coordinate systemhaving X, Y and Z axes corresponding to the axes of stereolithographysystem 10. However, other three-dimensional coordinate systems arecontemplated herein, including but not limited to polar, cylindrical andspherical.

In one form, gas turbine engine blade mold 12 is built at a buildorientation angle as measured from axis Z. The build orientation angleillustrated in FIG. 1 is zero degrees. Other build orientation anglesare fully contemplated herein. The three-dimensional coordinate systemis aligned with the build orientation angle. In one form the threedimensional coordinate system of mold 12 and stereolithography system 10coordinate system are coextensive.

Blade mold 12 is freeform fabricated by system 10 in layer-by-layerfashion by applying an energy dose to cure a film of ceramic-ladenphoto-polymerizable resin into a polymerized layer, applying a new filmof the resin, and applying an energy dose sufficient to bothphoto-polymerize the new film of resin into a new layer and to providean overcure to bind the new layer to the previous layer. In one form,each new resin film is formed over the topmost polymerized layer bylowering elevation changing member 26 to submerge the topmostpolymerized layer in the ceramic loaded resin 22 in reservoir 24. Inother embodiments, new layers of ceramic loaded resin 22 may be appliedto the topmost polymerized layer using other means. The process isrepeated to form a plurality of polymerized layers, i.e., layers ofceramic particles that are held together by a polymer binder, e.g., suchas the illustrated layer 14, 16, 18 and 20. The successively formedcured layers ultimately form the three-dimensional shape of gas turbineengine blade mold 12 having the desired three-dimensional featuresformed therein. As described herein, the three-dimensional features ofblade mold 12 include a controlled porosity distribution in portions ofthe mold.

In one form, each polymerized layer is on the order of 0.05 mm (0.002inches) thick, e.g., as measured along the Z axis, which may be referredto as the build direction. Thinner or thicker layers may be employed inother embodiments. For example, the thickness of each layer may varywith the needs of the particular application, including the desiredresolution of the finished mold 12. In some embodiments, some layers mayhave a greater thickness than other layers within the same mold Itshould understand that there is no intention herein to limit the presentapplication to any particular number of layers or thickness of layers.In addition, although only a single gas turbine engine blade mold 12 isillustrated, it will be understood that a plurality of gas turbineengine blade mold 12 may be formed as a batch in system 10.

In one form, the formation of the polymerized layers includes the use ofa leveling technique to level each of the layers of thephoto-polymerizable ceramic loaded resin prior to receiving the energyused to polymerize the resin. Examples of leveling techniques includeultrasonic processing; time delay; and/or a mechanically assisted sweep,such as the use of a wiper blade. The present application alsocontemplates embodiments that do not employ active leveling techniques.

The energy dose used to polymerize and overcure each layer may be variedor otherwise controlled. In one form, the energy dose is controlled byfixing a laser 28 power and beam 32 diameter, and then controlling thelaser scan speed (rate) across the resin surface. In another form, suchas with a flash cure system, the laser scan speed and laser power arereplaced with exposure time and lamp power. In yet another form, theparameters that control cure and overcure are lamp power and scan speed.In other embodiments, other energy sources maybe employed, e.g., UVsources. In various embodiments, other parameters may control cureand/or overcure.

After the formation of blade mold 12 in stereolithography system 10,blade mold 12 may be subjected to additional processing prior to use. Inone form, blade mold 12 is subjected to burnout processing and sinteringto yield an integral ceramic casting mold for creating a gas turbineengine blade casting. In other embodiments, blade mold 12 may not besubjected to burnout processing or may not be subjected to sintering. Inother embodiments, one or more of various techniques may be employed toremove polymeric material from blade mold 12, if desired, and/or toenhance the structural integrity of blade mold 12, if desired, e.g.,depending upon the particular application.

Referring now to FIGS. 2 and 3, a non-limiting example of blade mold 12in accordance with an embodiment of the present invention is depicted.In one form, blade mold 12 includes an airfoil portion 36, a platformportion 38, an attachment portion 40 and a cooling air passage core 42.In other embodiments, blade mold 12 may include other portions notmentioned herein, and/or may not include all of portions 36, 38 and 40.Cooling air passage core 42 extends in a spanwise direction 44 throughattachment portion 40. In one form, core 42 forms a single cooling airpassage in the blade casting produced using blade mold 12. In otherembodiments, core 42 may form a plurality of passages of variousorientations, which may or may not be interconnected. In one form, core42 extends through attachment portion 40 and terminates adjacent toplatform portion 38. In another form, core 42 extends further towardairfoil portion 36. In yet another form, core 42 extends through asubstantial portion of airfoil portion in spanwise direction 44. Inother embodiments, core 42 may extend completely through airfoil portion36. In still other embodiments, blade mold 12 may not include core 42.

Airfoil portion 36, platform portion 38 and attachment portion 40 arestructured to yield an airfoil, platform and attachment in the gasturbine engine blade casting. Portions of blade mold 12 include acontrolled porosity distribution 46. In one form, controlled porositydistribution 46 is a distribution of interconnected nodules 48 spacedapart by a plurality of interconnected pores 50 that are formed layer bylayer as part of blade mold 12. In one form, interconnected nodules 48and interconnected pores 50 are operable to form a metal foam or otherporous form with an open cell structure in selected portions of theblade casting produced using blade mold 12, e.g., in the airfoil. Inother embodiments, a closed cell structure may be formed in the castingby controlled porosity distribution 46. In one form, controlled porositydistribution 46 is generated by defining a desired form, such as thedesired geometric shapes, sizes and distribution of interconnectednodules 48 and interconnected pores 50. In one form, interconnectednodules 48 and interconnected pores 50 are defined electronically e.g.,using commercially available stereolithography computer aided design(CAD) software to generate an STL (.stl) file. The electronic definitionis then supplied to system 10, whereby scanning device 30 selectivelycures subsequent layers in order to yield the desired three-dimensionalinterconnected nodules 48 and interconnected pores 50 based on the STLfile.

In one form, blade attachment portion 40 operable to form a fully denseattachment in the blade casting, and hence, does not include acontrolled porosity distribution. It will be understood that in otherembodiments, controlled porosity distribution 46 may be incorporatedinto all or part of attachment portion 40. In one form, blade platformportion 38 operable to form a fully dense platform in the blade casting,and hence, does not include a controlled porosity distribution. Inanother form, blade platform portion 38 includes a controlled porositydistribution 46, e.g., to supply cooling air from the passage formed bycore 42 to the airfoil. It will be understood that in other embodiments,controlled porosity distribution 46 may be incorporated into all or partof platform portion 38.

A blade casting is produced using mold 12 by supplying a molten alloyinto mold 12, including directing the molten alloy into theinterconnected pores 50 of controlled porosity distribution 46. In oneform, the alloy is a nickel-based superalloy. In other embodiments,other alloys may be used, including aluminum alloys and titanium alloys.The molten alloy is then solidified, e.g., via cooling. In one form, themolten alloy is solidified in a controlled manner to yield a singlecrystal structure. In other embodiments, other crystalline structuresmay be obtained, including but not limited to directionally solidifiedand equiax crystal orientations. In some embodiments, the crystalstructure may not be controlled. Once the alloy is solidified, mold 12is removed to yield a cast metallic article in the form of a gas turbineengine blade casting. In one form, mold 12 is removed by leaching. In aparticular form, interconnected nodules 48 are removed by leaching toyield a blade casting with an airfoil having a plurality ofinterconnected pores extending therethrough.

Referring now to FIGS. 4 and 5, a non-limiting example of a bladecasting 60 produced using casting mold 12 in accordance with anembodiment of the present invention is depicted. In one form, bladecasting 60 is a turbine blade. In another form, blade casting 60 is acompressor blade. In yet another form, blade casting 60 is a fan blade.Blade casting 60 includes an airfoil 62, a platform 64, and anattachment 66 having a passage 68. Platform 64 is disposed betweenairfoil 62 and attachment 66. In one form, passage 68 is a cooling airpassage that extends through attachment 66 in spanwise direction 44toward airfoil 62. In other embodiments, passage 68 may extend in otherdirections in addition to or in place of direction 44. In still otherembodiments, blade casting 60 may be devoid of passages such as passage68. In one form, airfoil 62, platform 64 and attachment 66 areintegrally formed together as a unitary blade casting without the use ofbonds or joints using mold 12. In one form, blade casting 60 has adensity that varies with location in blade casting 60. In a particularform, blade casting 60 has a metallographic structure that ranges fromfully dense, e.g., in attachment 66, to porous, e.g., in airfoil 62.

In one form, controlled porosity distribution 46 in mold 12 forms aplurality of interconnected pores in blade casting 60 to yield a metalfoam 70 in blade casting 60. In a particular form metal foam 70 isformed in airfoil 62 and a portion of platform 64. In the depiction ofFIGS. 4 and 5, metal foam 70 is depicted in the form of “bubbles” ofvarying size. In one form, metal foam 70 has a porosity in the range of10 pores per inch to 100 pores per inch. In a particular form, theporosity ranges from 10 pores per inch to 60 pores per inch. In otherembodiments, other porosities may be utilized, including distributionsof pores of the same size. In one form, controlled porosity distribution46 yields a pore size in the blade casting 60 that decreases withincreasing proximity to an outer surface of the cast metallic article.For example, as depicted in FIGS. 4 and 5, pores 70A in a centralportion of airfoil 62 are of a larger size than pores 70B that areadjacent to an outer surface 72 of airfoil 62. In one form, the poresize in the metallic airfoil is largest in locations adjacent to thepassage 68 and transitions to the smallest pore size adjacent to outersurface 72 of airfoil 62. In one form, the plurality of interconnectedpores forming metal foam 70 have an open cell structure and are operableto transmit cooling air from passage 68 to outer surface 72 on airfoil62.

Referring now to FIGS. 6 and 7, a non-limiting example of a bladecasting 80 produced using casting mold 12 in accordance with anembodiment of the present invention is depicted. In one form, bladecasting 80 is a turbine blade. In another form, blade casting 80 is acompressor blade. In yet another form, blade casting 80 is a fan blade.Blade casting 80 includes an airfoil 82, a platform 84, and anattachment 86 having a plurality of passages 88. Platform 84 is disposedbetween airfoil 82 and attachment 86. In one form, passages 88 arecooling air passages that extend through attachment 86 in spanwisedirection 44 and passes through the bulk of airfoil 82. In otherembodiments, passages 88 may extend in other directions in addition toor in place of direction 44. In yet other embodiments, passages 88 mayextend completely through airfoil 82. In still other embodiments, bladecasting 80 may be devoid of passages such as passage 88. In one form,airfoil 82, platform 84 and attachment 86 are integrally formed togetheras a unitary blade casting without the use of bonds or joints using mold12. In one form, blade casting 80 has a density that varies withlocation in blade casting 80. In a particular form, blade casting 80 hasa metallographic structure that ranges from fully dense, e.g., inattachment 86, to porous, e.g., in airfoil 82.

In one form, controlled porosity distribution 46 in mold 12 forms aplurality of interconnected pores in blade casting 80 to yield a metalfoam 90 in blade casting 80. In a particular form, metal foam 90 isformed in airfoil 82, whereas platform 84 and attachment 86 are fullydense. In other embodiments, platform 84 and/or attachment 86 may not befully dense, but may have a controlled porosity, such as metal foam 90.In the depiction of FIGS. 6 and 7, metal foam 90 is depicted in the formof “bubbles” of varying size. In one form, metal foam 90 has a porosityin the range of 10 pores per inch to 100 pores per inch. In a particularform, the porosity ranges from 10 pores per inch to 60 pores per inch.In other embodiments, other porosities may be utilized, includingdistributions of pores of the same size. In one form, controlledporosity distribution 46 yields a pore size in the blade casting 80 thatdecreases with increasing proximity to an outer surface of the castmetallic article. For example, as depicted in FIGS. 6 and 7, pores 90Ain a central portion of airfoil 82 are of a larger size than pores 90Bthat are adjacent to an outer surface 92 of airfoil 82. In one form, thepore size in the metallic airfoil is the largest in locations adjacentto the passages 88 and transitions to the smallest pore size adjacent toouter surface 92 of airfoil 82. In one form, the plurality ofinterconnected pores forming metal foam 90 have an open cell structureand are operable to transmit cooling air from passages 88 to outersurface 92 in selected portions of airfoil 82. In one form, airfoil 82also includes a fully dense outer skin portion 94 that is devoid ofpores. In a particular form, fully dense skin portion 94 has a thicknessin the range of 0.005 inches to 0.030 inches. In other embodiments thathave a fully dense skin portion, other skin thickness values may beemployed. In one form, passages 88 are defined by ribs 96, which in someembodiments may be used to stiffen a hollow airfoil 82 and/or direct theflow of cooling air.

Because controlled porosity distribution 46 is explicitly defined andfreeform fabricated to generate the defined porosity distribution, someembodiments of the present invention may have fully dense portions thatseamlessly blend to a porous structure, such as a porous airfoil. Someembodiments of the present invention may provide a gradation ofproperties though the casting produced using mold 12. In one form,controlled porosity distribution 46 is used to produce an open cellstructure for use as cooling air passages, e.g., for transpirationcooling of the blade produced using mold 12. In one form, cooling aircan be bled into the passage(s) in the blade root (attachment) anddischarged through the outer skin of the airfoil and/or other portionsof the blade. This may include cooling the structure through convection,and discharging the air through the outer skin to shield the exteriorsurface of the blade from hot engine gases. In one form, the outer skincan have varying density to control cooling air flow and direction. Inaddition, by freeform fabricating the size and shape of the pores, theamount of cooling can be controlled. Further, the metal foam could beopen in some portions of the blade, e.g., the pressure side of theairfoil, and closed in other portions of the blade, e.g., the suctionside of the airfoil.

Embodiments of the present invention include a method for forming aporous article, comprising: freeform fabricating a ceramic mold having acontrolled porosity distribution; sintering the ceramic mold; supplyinga molten alloy to the sintered mold; and removing the ceramic mold toyield a cast metallic article.

In a refinement, the cast metallic article has a density that varieswith location in the cast metallic article.

In another refinement, the controlled porosity distribution in theceramic mold forms a metal foam in a portion of the cast metallicarticle.

In yet another refinement, the metal foam has a porosity in the range of10 pores per inch to 100 pores per inch.

In still another refinement, the controlled porosity distribution yieldsa pore size in the cast metallic article that decreases with increasingproximity to an outer surface of the cast metallic article.

In yet still another refinement, the cast metallic article is a gasturbine engine blade; wherein the gas turbine engine blade includes anairfoil and an attachment structured to secure the airfoil to a gasturbine engine disc; wherein the attachment is fully dense; and whereinthe airfoil has a controlled distribution of pores.

In a further refinement, the gas turbine engine blade includes aplatform disposed between the attachment and the airfoil.

In a yet further refinement, the attachment includes a passage extendingtherethrough toward the airfoil.

In a still further refinement, the passage extends at least partiallythrough the airfoil in a spanwise direction.

In a yet still further refinement, the ceramic mold is freeformfabricated to yield an open cell structure in at least one portion ofthe cast metallic article.

Embodiments of the present invention also include a method for forming agas turbine engine blade casting, comprising: defining a distribution ofinterconnected nodules spaced apart by a first plurality ofinterconnected pores; freeform fabricating a ceramic mold, the ceramicmold including an airfoil portion having the defined distribution ofinterconnected nodules spaced apart by the first plurality ofinterconnected pores; supplying a molten alloy to the ceramic mold;solidifying the molten alloy; and leaching the interconnected nodules toyield a metallic airfoil having a second plurality of interconnectedpores extending therethrough.

In a refinement, the supplying the molten alloy to the ceramic moldincludes directing the molten alloy into the first plurality ofinterconnected pores of the ceramic mold.

In another refinement, a pore size in the metallic airfoil is in therange of 10 pores per inch to 100 pores per inch.

In yet another refinement, the embodiment further includes freeformfabricating the ceramic mold to include a blade platform portion that isoperable to form a blade platform in the blade casting, wherein theblade platform is integrally formed with the metallic airfoil.

In still another refinement, the embodiment further includes freeformfabricating the ceramic mold to include an attachment portion that isoperable to form a fully dense attachment in the blade casting, whereinthe attachment is integrally formed with the metallic airfoil.

In yet still another refinement, the embodiment further includesfreeform fabricating the ceramic mold to form a passage in blade castingthat extends in a spanwise direction through the attachment toward themetallic airfoil.

In a further refinement, a pore size in the metallic airfoil is alargest pore size in locations adjacent to the passage and transitionsto a smallest pore size adjacent to an outer surface of the metallicairfoil.

In a yet further refinement, the second plurality of interconnectedpores are operable to transmit a fluid from the passage to an outersurface of the blade casting.

In a still further refinement, the outer surface is an outer surface ofthe metallic airfoil.

In a yet still further refinement, the embodiments further includesfreeform fabricating the ceramic mold to form a passage in the bladecasting that extends through the attachment and at least partiallythrough the metallic airfoil in a spanwise direction; and wherein a poresize in the metallic airfoil is a largest size in locations adjacent tothe passage and transitions to a smallest size in locations adjacent toan outer surface of the metallic airfoil.

In an additional refinement, the metallic airfoil includes a centralportion having a largest pore size; and wherein a pore size transitionsto a smallest pore size adjacent an outer surface of the metallicairfoil.

In another additional refinement, the metallic airfoil includes a fullydense outer skin portion.

Embodiments of the present invention also include a method for forming agas turbine engine blade casting, comprising: means for forming a moldhaving a plurality of interconnected nodules; supplying a molten alloyto the mold; and means for removing the plurality of interconnectednodules to yield a metallic airfoil having a plurality of interconnectedpores extending therethrough.

In a refinement, a density of the metallic airfoil varies with locationin the metallic airfoil.

While the invention has been described in connection with what ispresently considered to be the most practical and preferred embodiment,it is to be understood that the invention is not to be limited to thedisclosed embodiment(s), but on the contrary, is intended to covervarious modifications and equivalent arrangements included within thespirit and scope of the appended claims, which scope is to be accordedthe broadest interpretation so as to encompass all such modificationsand equivalent structures as permitted under the law. Furthermore itshould be understood that while the use of the word preferable,preferably, or preferred in the description above indicates that featureso described may be more desirable, it nonetheless may not be necessaryand any embodiment lacking the same may be contemplated as within thescope of the invention, that scope being defined by the claims thatfollow. In reading the claims it is intended that when words such as“a,” “an,” “at least one” and “at least a portion” are used, there is nointention to limit the claim to only one item unless specifically statedto the contrary in the claim. Further, when the language “at least aportion” and/or “a portion” is used the item may include a portionand/or the entire item unless specifically stated to the contrary.

1. A method for forming a porous article, comprising: freeformfabricating a ceramic mold having a controlled porosity distribution;sintering the ceramic mold; supplying a molten alloy to the sinteredmold; and removing the ceramic mold to yield a cast metallic article. 2.The method of claim 1, wherein the cast metallic article has a densitythat varies with location in the cast metallic article.
 3. The method ofclaim 1, wherein the controlled porosity distribution in the ceramicmold forms a metal foam in a portion of the cast metallic article. 4.The method of claim 3, wherein the metal foam has a porosity in therange of 10 pores per inch to 100 pores per inch.
 5. The method of claim1, wherein the controlled porosity distribution yields a pore size inthe cast metallic article that decreases with increasing proximity to anouter surface of the cast metallic article.
 6. The method of claim 1,wherein the cast metallic article is a gas turbine engine blade; whereinthe gas turbine engine blade includes an airfoil and an attachmentstructured to secure the airfoil to a gas turbine engine disc; whereinthe attachment is fully dense; and wherein the airfoil has a controlleddistribution of pores.
 7. The method of claim 6, wherein the gas turbineengine blade includes a platform disposed between the attachment and theairfoil.
 8. The method of claim 6, wherein the attachment includes apassage extending therethrough toward the airfoil.
 9. The method ofclaim 8, wherein the passage extends at least partially through theairfoil in a spanwise direction.
 10. The method of claim 1, wherein theceramic mold is freeform fabricated to yield an open cell structure inat least one portion of the cast metallic article.
 11. A method forforming a gas turbine engine blade casting, comprising: defining adistribution of interconnected nodules spaced apart by a first pluralityof interconnected pores; freeform fabricating a ceramic mold, theceramic mold including an airfoil portion having the defineddistribution of interconnected nodules spaced apart by the firstplurality of interconnected pores; supplying a molten alloy to theceramic mold; solidifying the molten alloy; and leaching theinterconnected nodules to yield a metallic airfoil having a secondplurality of interconnected pores extending therethrough.
 12. The methodof claim 11, wherein said supplying the molten alloy to the ceramic moldincludes directing the molten alloy into the first plurality ofinterconnected pores of the ceramic mold.
 13. The method of claim 11,wherein a pore size in the metallic airfoil is in the range of 10 poresper inch to 100 pores per inch.
 14. The method of claim 11, furthercomprising freeform fabricating the ceramic mold to include a bladeplatform portion that is operable to form a blade platform in the bladecasting, wherein the blade platform is integrally formed with themetallic airfoil.
 15. The method of claim 11, further comprisingfreeform fabricating the ceramic mold to include an attachment portionthat is operable to form a fully dense attachment in the blade casting,wherein the attachment is integrally formed with the metallic airfoil.16. The method of claim 15, further comprising freeform fabricating theceramic mold to form a passage in blade casting that extends in aspanwise direction through the attachment toward the metallic airfoil.17. The method of claim 16, wherein a pore size in the metallic airfoilis a largest pore size in locations adjacent to the passage andtransitions to a smallest pore size adjacent to an outer surface of themetallic airfoil.
 18. The method of claim 16, wherein the secondplurality of interconnected pores are operable to transmit a fluid fromthe passage to an outer surface of the blade casting.
 19. The method ofclaim 18, wherein the outer surface is an outer surface of the metallicairfoil.
 20. The method of claim 11, further comprising freeformfabricating the ceramic mold to form a passage in the blade casting thatextends through the attachment and at least partially through themetallic airfoil in a spanwise direction; and wherein a pore size in themetallic airfoil is a largest size in locations adjacent to the passageand transitions to a smallest size in locations adjacent to an outersurface of the metallic airfoil.
 21. The method of claim 11, wherein themetallic airfoil includes a central portion having a largest pore size;and wherein a pore size transitions to a smallest pore size adjacent anouter surface of the metallic airfoil.
 22. The method of claim 11,wherein the metallic airfoil includes a fully dense outer skin portion.23. A method for forming a gas turbine engine blade casting, comprising:means for forming a mold having a plurality of interconnected nodules;supplying a molten alloy to the mold; and means for removing theplurality of interconnected nodules to yield a metallic airfoil having aplurality of interconnected pores extending therethrough.
 24. The methodof claim 23, wherein a density of the metallic airfoil varies withlocation in the metallic airfoil.